A reflection type projecting screen includes a diffuse plate having a diffuse transmission surface for converting at least transmission light into diffused light and a corner cube array for reflecting the light passing through the diffuse plate to a position which is approximately similar to a passing position of the diffuse transmission surface. A first rotary seal is frictionally fit on the shaft adjacent the first stationary seal seat. A laser scanner is attached to at least on one side of the chassis. In one embodiment, the threshold is related to a prioritized Bit Rate or a bucket Size Duration or both. The control circuit switches the first and second switches onoff simultaneously to make a sum of absolute values of voltages at the negative and positive voltage output terminals a predetermined voltage value. Alternatively, the method comprises placing a guide catheter into the coronary sinus, threading a guide wire into the coronary veins, pushing the lead over the guide wire and into the coronary sinus or the coronary vein, and sensing and pacing the heart via the lead in its implanted site in the coronary sinus or the coronary vein.